Effects of cyclin-dependent kinase 8 specific siRNA on the proliferation and apoptosis of colon cancer cells.

BACKGROUND: To investigate the expression of cyclin-dependent kinase 8 (CDK8) and ß-catenin in colon cancer and evaluate the role of CDK8 in the proliferation, apoptosis and cell cycle progression of colon cancer cells, especially in HCT116 cell line. METHODS: Colon cancer cell line HCT116 was transfected with small interfering RNA (siRNA) targeting on CDK8. After CDK8-siRNA transfection, mRNA and protein expression levels of CDK8 and ß-catenin were determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot assay in HCT116 cells. Cell proliferation was measured by 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide Methylthiazolyl tetrazolium (MTT) assay, and cell cycle distribution and apoptosis were analyzed by flow cytometry analysis (FACS). CDK8 and ß-catenin protein levels were also examined by real-time PCR and immunohistochemistry (IHC) in colon cancer tissues and adjacent normal tissues. RESULTS: After CDK8 specific siRNA transfection, mRNA and protein expression levels of CDK8 and ß-catenin in HCT116 cells were noticeably decreased (P < 0.05). CDK8 specific siRNA transfection inhibited HCT116 cells' proliferation and facilitated their apoptosis significantly (P < 0.05). In addition, the proportion of HCT116 cells in the G0/G1 phase was remarkably increased after CDK8-siRNA transfection (P < 0.05). The expression levels of CDK8 and ß-catenin in adjacent normal tissues were lower than in tumor tissues (P < 0.05). Moreover, the expression of CDK8 was correlated with the expression of ß-catenin in both tumor and adjacent normal tissues (P < 0.05). CONCLUSIONS: CDK8 and ß-catenin were expressed in colon cancer at a high frequency. CDK8 specific siRNA transfection down-regulated the expression of CDK8 in colon cancer cells, which was also associated with a decrease in the expression of ß-catenin Moreover, CDK8 specific siRNA inhibited the proliferation of colon cancer cells, promoted their apoptosis and arrested these cells in the G0/G1 phase. Interference of CDK8 might be an effective strategy through ß-catenin regulation of colon cancer.

Effect of recombinant adenovirus vector mediated human interleukin-24 gene transfection on pancreatic carcinoma growth.

BACKGROUND: Pancreatic cancer is a highly malignant tumor affecting an ever increasing number of patients with a mean 5-year survival rate below 4%. Therefore, gene therapy for cancer has become a potential novel therapeutic modality. In this study we sought to determine the inhibitory effects of adenovirus-mediated human interleukin-24 (AdhIL-24) on pancreatic cancer. METHODS: Human interleukin-24 gene was cloned into replication-defective adenovirus specific for patu8988 tumor cells by virus recombination technology. Reverse transcription-polymerase chain reaction and Western blotting analysis were used to determine the expression of human interleukin-24 mRNA in patu8988 cells in vitro. Induction of apoptosis by overexpression of human interleukin-24 in patu8988 cells was determined by flow cytometry. In vivo efficacy of adenoviral delivery of human interleukin-24 was assessed in nude mice (n = 10 for each group) bearing patu8988 pancreatic cancer cell lines by determining inhibition of tumor growth, endothelial growth factor and CD34 expression, and intratumoral microvessel density (MVD). RESULTS: The recombinant adenovirus vector AdVGFP/IL-24 was constructed with a packaged recombinant retrovirus titer of 1.0 x 10(10) pfu/ml and successfully expressed of both mRNA and protein in patu8988 cells. The AdVGFP/IL-24 induced apoptosis of patu8988 tumor cells in vitro and significantly inhibited tumor growth in vivo (P < 0.05). The intratumoral MVD decreased significantly in the treated tumors (P < 0.05). CONCLUSION: The recombinant adenovirus AdGFP/IL-24 can effectively express biologically active human interleukin-24, which results in inhibition of pancreatic cancer growth.

Inhibition of pancreatic carcinoma cell growth in vitro by DPC4 gene transfection.

AIM: To detect the expression of DPC4 in malignant and non-malignant specimens of human pancreas, and observe the inhibition of retroviral pLXSN containing DPC4 on pancreatic carcinoma cells in vitro. METHODS: The expression of DPC4 was determined in 40 pancreatic adenocarcinoma and 36 non-malignant pancreatic specimens by reverse-transcriptase polymerase chain reaction (RT-PCR) and immunohisto-chemistry. Furthermore, we constructed retroviral vectors containing DPC4, which then infected the pancreatic carcinoma cell line BxPC-3. Cell growth in vitro after being infected was observed, and the vascular endothelial growth factor (VEGF) mRNA level in the daughter cells was determined by semi-quantitative PCR assay. RESULTS: The RT-PCR assay showed a positive rate of DPC4 mRNA in 100% (36/36) of normal specimens, compared to 40% (16/40) in adenocarcinoma specimens. The regional and intense positive cases of DPC4 expression in adenocarcinoma detected by immunohistochemistry were 10 and four, whereas it was all positive expression in normal tissues. There was a significant difference of DPC4 expression between them. The stable expression of DPC4 in the pancreatic carcinoma cells BxPC-3 could be resumed by retroviral vector pLXSN transfection, and could inhibit cell growth in vitro. Rather, DPC4 could decrease VEGF mRNA transcription levels. CONCLUSION: The deletion of DPC4 expression in pancreatic carcinoma suggests that loss of DPC4 may be involved in the development of pancreatic carcinoma. The retroviral vector pLXSN containing DPC4 can inhibit the proliferation of pancreatic carcinoma cells, and down-regulate the level of VEGF.

Role of CD80 in stimulating T lymphocyte activation.

AIM: To observe biological characteristics of hepatocarcinoma cells before and after CD80 transfection and to compare the effect of CD80-transfected hepatocarcinoma cells on T lymphocyte activation. METHODS: Retro virus vector carrying CD80 gene was transfected into HepG2 cells to establish CD80-transfected hepatocarcinoma cells (HepG2/hCD80). Flow cytometry (FCM) was performed to detect CD80 expression in the transfected cells. RT-PCR was used to evaluate CD80 expression at mRNA level. In the presence of anti-CD3 mAb, the proliferation of T lymphocyte was observed by MTT. Meanwhile, the expression of activated molecule marker CD25 was analyzed through FCM. RESULTS: A stable cell line HepG2/hCD80 expressing the human CD80 was established. Growth curve showed that the molecule CD80 could obviously decrease the growth of tumor cells. HepG2/hCD80 was evidenced to have a potency to enhance T cell proliferation and upregulate CD25 expression. CONCLUSION: CD80 transfection can lower malignant phenotype of hepatocarcinoma cells. CD80 transfection has a down-regulatory effect to activated T cells in vitro.

[Construction of recipient strain of expression-secretion system in filamentous fungi].

Glucoamylase overproducing A. niger T21 was mutated by UV mutagensis. An extracellular acid protease-deficient mutant, A. niger T21-201, which produced only 0.76% extracellular acid protease activity of the parent strain, was screened by casein-degradating plate and determination of protease activity. Moreover, the growth properties and the ability to secrete glucoamylase of A. niger T21-201 are identical to these of starting strain T21. The comparison of expression-secretion levels of heterologous gene in A. niger T21-201 and T21 was carried out with bacterial vhb as reporter, the level of expression-secretion of VHb in A. niger T21-201 was 6-7 times higher than that in T21, but the transcriptional levels of vhb gene in both strains were similar revealed by Northern blot. Therefore, it was demonstrated that the deficiency of acid protease of recipient T21-201 has significant effect on the protection of heterologous protein.